Thanks guys! There is a reason I always come to this site first.
Had a system that was massively messed up because of an anti-virus issue, so tried to do system restore. System restore failed repeatedly, so tried to do clean install. Clean install from USB didn't work with x64 or x86 versions that I have, although both have worked before. Kept getting 0x80070017 error even after wiping HD etc. Was about to jump out a window. Then tried the RAM swap, and it works!
If you are having the 0x80070017 error on install, take out a RAM stick and try again, then if it still doesn't work, try the other one. It works!